Thin film transistors (TFTs) with amorphous zinc tin oxide (ZTO) channel layer were fabricated by a simple and low-cost solution process. The ZTO thin films are highly transparent (>90% transmittance) in the visible region. The ZTO TFTs fabricated at 400 and 500 • C are operated in enhancement mode. The TFT annealed at 500 • C shows a mobility of 14.11 cm 2 V −1 s −1 , a threshold voltage of 1.71 V, a subthreshold slope of 0.4 V dec −1 and an on-off current ratio greater than 10 8. In addition, we investigated the gate bias stability of the TFT. Positive gate bias results in a positive shift of the threshold voltage due to the charge trapping in the channel/dielectric interface.

No abstract

Ultra-definition, large-area displays with three-dimensional visual effects represent megatrend in the current/future display industry. On the hardware level, such a “dream” display requires faster pixel switching and higher driving current, which in turn necessitate thin-film transistors (TFTs) with high mobility. Amorphous oxide semiconductors (AOS) such as In-Ga-Zn-O are poised to enable such TFTs, but the trade-off between device performance and stability under illumination critically limits their usability, which is related to the hampered electron-hole recombination caused by the oxygen vacancies. Here we have improved the illumination stability by substituting oxygen with nitrogen in ZnO, which may deactivate oxygen vacancies by raising valence bands above the defect levels. Indeed, the stability under illumination and electrical bias is superior to that of previous AOS-based TFTs. By achieving both mobility and stability, it is highly expected that the present ZnON TFTs will be extensively deployed in next-generation flat-panel displays.

Transparent thin-film transistors ͑TTFTs͒ with an indium-zinc oxide ͑IZO͒ active layer by the solution-processed deposition method were fabricated and their TFT characterization was examined. Solution-processed IZO thin films were amorphous and highly transparent with Ͼ90% transmittance in the visible region with an optical bandgap of 3.1 eV. Spin-coated IZO TTFTs were operated in depletion mode and showed a field-effect mobility as high as 7.3 cm 2 /V s, a threshold voltage of 2.5 V, an on/off current ratio greater than 10 7 , and a subthreshold slope of 1.47 V/decade. Metal-oxide thin films have been traditionally used as insulators, dielectrics, and conductors in ͑opto͒electronic devices. Recently, metal-oxide thin films have been intensively studied to be applied as transparent semiconducting active layers in transparent thin-film transistors ͑TTFTs͒. Transparent oxide semiconductors ͑TOSs͒ have many advantages compared to silicon or organic semiconductors. TOSs are transparent in the visible region due to their large bandgap and have environmental stability and high field-effect mobility comparable to that of polycrystalline silicon. 1,2 Many TOSs such as ZnO, 3,4 zinc-tin oxide ͑ZTO͒, 5,6 indium-zinc oxide ͑IZO͒, 7-9 and indium-gallium-zinc oxide ͑IGZO͒ 2,10,11 have been reported for transparent active-channel materials in TTFTs. Several TTFTs using TOSs 12,13 and even fully transparent flexible structures 3,14 have been reported. TTFTs based on TOSs are considered to be an alternative to amorphous Si TFTs. However, TOSs are generally prepared by vacuum-deposition methods such as rf magnetron sputtering and pulsed laser deposition. Vacuum-deposition methods require expensive equipment and result in high manufacturing costs.Solution-processed thin-film deposition methods could offer many advantages such as simplicity, low cost, and high throughput that enable the fabrication of high-performance and low-cost electronics. In addition, solution-processed deposition methods such as screen printing, inkjet printing, and imprinting offer the possibility of the direct patternability of TOS thin films which could replace the conventional photolithographic technique. Recently, ZnO, 15-17 ZTO, 18 and IZO-based 19 TTFTs fabricated by solution-processed deposition using metallorganic or metal halide precursors in various solvents were reported to have high mobility up to ϳ16 cm 2 /V s and to give direct patternability. However, in the case of using metal chloride as precursors, the presence of chloride ions during heattreatment of the film is unfavorable under certain circumstances. In addition, TTFTs fabricated by solution-processed deposition showed high off currents and a low on/off current ratio compared to the vacuum-deposited TTFTs.In this article, we report the amorphous IZO semiconductor thin films fabricated by solution process under ambient air conditions using metal acetates as precursors and the performance of TTFTs with an amorphous IZO active layer. Spin-coated IZO thin film was uniform, highly transparent...

Many studies have been performed recently in an attempt to produce full-color phosphors, [1][2][3] especially those with white color emissions, [4] due to their important role in the field of display systems and lighting technologies. Various colors can be achieved by adjusting the relative red, green and blue luminescent components. Thus, full-color phosphors could be obtained by controlling the relative amounts of these components to achieve multicolored photoluminescence. The sharp and intense line-emissions of rare earth (RE) complexes have been of great interest in the luminescence material science field. [1,5] In the RE complex, an organic ligand is employed as an energy absorption antenna to photosensitize the RE ion in the center of the complex. The trivalent RE ion absorbing the energy can exhibit a highly efficient and narrow emission via an effective intermolecular energy transfer from the ligand to the luminescent center. [6] In addition, some ligands like salycilic acid show strong blue emission under UV excitation. This suggests that some organic ligands can serve as blue components in addition to being photosensitizers. Among RE complexes, trivalent europium (Eu) and terbium (Tb) ions exhibit bright red and green emissions when they are linked to a suitable ligand. Therefore, Eu and Tb complexes accompanied by excess blue light emitting ligands can be co-doped and served as red, green, blue luminescent components for multicolored photoluminescence. The color can be controlled by changing the composition of the RE ions and the photosensitizers which affect the energy transfer to the various components resulting in a full-color phosphor. Recently, Wada et al. reported the multicolored photoluminescence of zeolite powders incorporated with Tb 3+ and Eu 3+ ions and photosensitizers exhibiting red-green-blue (RGB) photoluminescence.[1] The color was finely tuned by changing the composition of the RE ions and the photosensitizers, the temperature, and the excitation wavelength. However, a white color was only observed at a temperature of 77 K. In this paper, we present mesophase silicate thin films incorporated with RE ions and organic ligands that successfully exhibit multicolored photoluminescence including white at room temperature. The use of ordered mesophase silicate thin film as a matrix material in which to incorporate photoactive molecules is attracting increasing interest. [7][8][9] In the present study, RE complexes are incorporated into films of this type. The luminescent dopants can easily be incorporated into nano-sized mesopores to obtain homogeneous thin films. The rigid inorganic framework, which can protect the dopants in the silicate mesophase matrix, can improve the stability of the RE complexes. Also, the advantages of using the silicate mesophase matrix to incorporate the complexes include the local separation of organic/inorganic regions, the prevention of dopant aggregation, the chemical inertness and the controllable porosity of the silicate framework.[9] Furthermore, the hydrop...